Apparatus for use with telephone mouthpieces



Dec. 17, 1940. 2,225,509

H. SCHOBER, MAIDEN-NAME MOERDER APPARATUS FOR USE WITH TELEPHONEMOUTHPIECES Filed Nov. 17, 1937 2 Sheets-Sheet l Dec. 17, 1940.2,225,509

' H. SCHOBER, MAIDEN-NAME MOERDER APPARATUS FOR USE WITH TELEPHONEMQUTHPIECES Filed Nov. 17, 1937 2 Sheets-Sheet 2 lNl/EN 7-02.

Patented Dec. 17, 1940 PATENT OFFICE APPARATUS FOR USE WITH 'iELERHONMOUTHPIECES Helene Schober, maiden-name Moerder, Berlin, GermanyApplication November 1'1,

1937, Serial No. 174,938

In Germany November 21, 1936 3 Claims. (01. 181-34) This inventionrelates to sound muflling appliances attached to the mouthpieces of thetransmitters of telephones, whereby sound to be transmitted through suchmouthpieces, though not impaired'in transmission, is not heard bypersons located in the vicinity of the transmitter.

It is an object of the invention to improve the quality of the soundsimpressed upon the transmitter and at the same time to reduce the trans-19 mission of sound waves into the room wherein the speaker is located.

.Anotherobject of the'invention is to provide an apparatus which may beused interchangeably with diiferent transmitters and which, when not 15in use, can be collapsed to a very small space so as to assumevest-pocket size.

According to this invention, the device comprises a tubular body adaptedto provide an acoustic connection between the mouth of the 20 speakerand the transmitter and an acoustic filter at the mouthpiece of thetubular body, said filter having a damping range comprising thefrequency range of the speech transmission.

The term acoustic filter, as used in the present specification, isintended to define an arrangement providing one or more hollow spaces,the size, material and apertures of which are such that a predeterminedrange of acoustic frequencies only is damped by the filter while other30 frequencies are allowed to pass practically unattenuated. The lawsaccording to which such acoustic filters have to be designed in order toattenuate a predetermined frequency range are well known in the art,therefore it will not be necessary to present a detailed description.

The invention will be better understood by reference to the followingdetailed description in connection with the accompanying drawingsshowing schematically by way of example some 40 preferred embodiments ofthe invention, and

wherein:

Figure 1 is a longitudinal section of an ap paratus constructed inaccordance with the invention,

45 Figure 2, is a fragmentary sectional view of the end portion of amodified form of a device according to Fig. 1,

Figure 3 is a fragmentary sectional view of an apparatus with adetachable end rim, 50 Figure 4 is a fragmentary sectional'view showinga detail,

Figure 5 is a side view, partly in section, of a collapsible apparatusin operative position,

Figure 6 is a side view of the apparatus shown 5 in Figure 5, incollapsed condition,

Figure 7 is a side view, partly in section of an apparatus including anadditional sound amplifier in the sound transmission channel,

Figure 8 is a side view, partly in section, of a preferred constructionof a device according to ,5 the invention. I

Referring to the drawings in greater detail, the bent tubular body Iaccording to Figure 1 forms a sound conducting channel and may consistof sheet metal, artificial resin or other suit- 10 able light material.The upper portion of the said tubular body I is constituted by a double-Walled cylindrical member 2 which forms an acousticfilter and isprovided with a mouthpiece or rim 3. The member 2 and rim 3 may beintegrally formed of rubber or a similar suitable fiexiblesound-absorbing material. According to the right hand half of Figure 1,the member 2 is connected to the body I by a double-fold connection 4,while according to the left hand half so of Figure 1, the member 2 isconnected to the body I by a single-fold connection 5. The cylindricalportion 2 has a hollow space in which there is arranged a resilienthelical spring tending to stretch or spread the portion 2. Thecylindrical portion 2 has longitudinal slits I in its inner wall whichslits are distended or opened as the mouthpiece 3 engages the mouth ofthe speaker. Apertures 8 of smaller size and/or less number than theslits I are provided in the outer .wall of the cylindrical double-walledportion 2.

- The rim 3 is made hollow to form a resilient edge which readily adaptsitself to the mouth of the user. 1

Further apertures 9 are provided in the bent tubular body I tofacilitate the discharge of the air current accompanying the humanspeech.

.These apertures 9 are covered by members III which may consist ofsponge rubber or may take the form of small acoustic filters orlabyrinths, thereby permitting the air to escape while the sound wavesare absorbed or damped or mutilated in such-v a manner as to becomeunintelligible'to persons in the vicinity of the telephone transmitter;

Fitted to the transmitter-end of the body I is a resilient ring II, forinstance of rubber which may be secured. to the tubular body I by a foldconnection with its inner face adapted to engage the microphone I2 ofthe telephone transmitter ,59 indicated by dotted lines. I

. It will be understood that in operation the sound waves emitted fromthe speakers mouth pressed against rim 3 will pass through thecylindrical portion 2 without substantial reflection g at the wallsthereof, since these walls form an acoustic filter or consist ofsound-absorbing ma terials while the air currents produced by the speechare discharged through the slits 1 and ports 8. Furthermore, in view ofthe fact that the cylindrical portion 2 represents an acoustic filtercapable of damping certain frequencies, the frequencies which are notwithin the cut-off range of the filter, more particularly the highnotes, can readily pass through the portion 2 and the bent portion I tothe transmitter l2, while the frequencies within the cut-off range ofthe filter 2, more particularly the low notes, are damped or attenuatedby the filter and thus act upon the transmitter with a reducedintensity.

As a result of this effect of the filter 2, a smooth and cleartransmission is ensured and the impression of a closed resonance chamberobtained with the known devices of this kind is obviated. On the otherhand, the speech vibrations, if reasonably reduced in sound intensityare not transmitted to the air outside the device 1, 2, but onlyunintelligible sounds, if anything can be noticed by bystanders.

A practical design of the acoustic filter 2 is shown in Figure 2,comprising a number of superposed hollow rings 14. The rings may consistof rubber and may be joined by a common vulcanizing process. The hollowrings 13 have inner ports l4 and outer ports I 5 the latte-r being fewerin number and/or smaller than theports l4. Further ports l6 are providedto connect the individual hollow spaces. The flexible top ring I 3serves to effect tight contact and good adaptation to the mouth of thespeaker.

The acoustic filter 2 which in Figure 2 is formed by the superposedhollow rings 13, should always be arranged immediately adjacent to themouthpiece so as to substantially avoid the production of detrimentalreflections.

Figure 3 illustrates a detachable or interchangeable mouthpiece,comprising a resilient hollow ring IT for instance of rubber attached toa sheet metal ring I8 stiffened by spot-welding at the points I9. Thesheet metal ring 18 engages a ring 22 secured to the filter chamber 2|by forcing the rubber edges of the latter between the lower spread edgeportions of ring 22 having their upper portions secured together byspot-welding at the points 22. The faces of the parts l9 and engagingeach other are slightly tapering to ensure tight engagement and easyinterchange.

Referring to Figure 4, illustrating a fragmentary section of the bentportion I, it will be seen that longitudinal slits 35 are providedcovered by a cap 36 having portholes 31. The cap 36 is advantageouslyfilled with viscose, sponge rubber, felt, reticular or similar dampingmaterial as shown at IO, Figure 1, so that the chamber thus formedserves as an additional muffler.

Referring to the embodiment according to Figure 5, the bent tubular body25 of the device is constructed to be readily collapsible. To this end,it consists of rubber or impregnated fabric which in the operatingposition is spread by a helical spring 26 compressed and held togetheron one side by a clamp or the like as shown at 27 while in thenon-operating position it can be collapsed to occupy a small space asshown in Figure 6 in that the walls of the device fold togetherconcertina-fashion. A bracket or double-hock 28 may serve to hold thespring 26 in the compressed state. The filter portion 23 and theconnecting portion 24 may be formed in any suitable manner in accordancewith this invention.

I have found that the satisfactory transmission of speech is largelydependent on the upper frequencies of the audible spectrum. In order toimprove the transmission of these upper frequencies while withholdingthe low frequencies I contemplate to use a device as illustrated inFigure 7, in which a selective frequency amplifier is embodied. Thisamplifier comprises a very small microphone 3| and a telephone 32 bothbeing connected by a metallic tube 34 and an insulated conductor 33through a battery 38 which may be. connected by a push-button 39. Themicrophone 3land telephone 32 are so designed that they receive, amplifyand reproduce the higher speech frequencies only, thus improving thearticulate and clear transmission which depends on the faithful andeflicient reproduction of the higher frequencies.

A preferred form of my novel device is shown in Figure 8. A mouldedtubular angle piece 40 of artificial resin, such as aphenol-formaldehyde condensation product, ebonite or the like, isprovided at both ends with coupling means adapted to connect the anglepiece 40 with the transmitter of a hand-set telephone on the one handand to associate it with the mouth of the speaker on the other hand. Tothis end, the transmitter end of the piece 40 has a collar 4| adapted toreceive a rubber sleeve 42 which is normally in a tubular form and spunwith its free end over the collar 4|, so as toengage the outer surfaceof the piece 40 with its collar 43. A sponge rubber or other resilientinsert 44 may be provided between the throat of the tube 40 and thesleeve 42 to make up for possible inaccurate fitting and to ensure tightengagement between the tube 40 and sleeve 42. In this manner, the devicecan be readily attached to the transmitter and detached therefrom.

The upper end of the angle piece 40 is formed with an annular groove 45adapted to receive the filter 46. The filter 46 consists of adoublewalled rubber sleeve turned over at 47 and held together at 48 andformed with a collar at 49 to provide two communicating chambers in thelower of which is disposed a, helical spring 49 tending to hold thesleeve in shape. Five sets of four ports 50 each are arranged in theinner wall and five single ports 5| are provided in the outer wall in astaggered relation to the ports 50. In View of the resiliency of thematerial, the sleeve 45, when forced into the groove 45, will be heldtherein by friction and the sleeve 46 will readily adapt itself to themouth of the user by assuming a corrugated form as indicated in the lefthand side of Figure 8.

The angle piece 43 is provided with two longitudinal slots 52 covered bya cap 53 secured thereto by screws. The hollow space thus formed isfilled with sponge rubber 54 or a similar soundabsorbing material.

A paper ring 55 may or may not be placed over the mouth piece 43, so asto prevent direct contact with the latter and for sanitary anddisinfecting purposes.

While I have herein shown and described certain preferred embodiments ofmy invention, I wish it to be understood that I do not confine myself toall the precise details herein set forth by way of illustration, asmodification and variation may be made without departing from the spiritof the invention or exceeding the scope of the appended claims.

I claim:

1. In a device of the character described, a rigid tubular memberadapted to have one end thereof detachably secured to the opening of atelephone transmitter, a mouthpiece secured to the other end of saidmember being constituted by a double walled sleeve of easily yieldingmaterial capable of adapting itself to the mouth of a user, said sleeveforming a closed annular chamber and having portholes in the inner andouter walls thereof, the portholes in one wall of said sleeve beingstaggered relative to the portholes in the opposite wall of the sleevethereby to form an acoustic filter capable of absorbing vibratory airpressure Variations while allowing steady air currents to pass to theoutside, and resilient stiffening means disposed between the walls of aportion of said sleeve adjacent to said tubular member.

2. In a device of the character described, a rigid tubular memberadapted to have one end thereof detachably secured to the opening of atelephone transmitter, a. mouthpiece secured to the other end of saidmember being constituted by a double walled rubber sleeve forming aclosed annular chamber having portholes in its inner and outer wallportions adjacent to said tubular member, the portholes in one wall ofsaid sleeve being staggered relative to the portholes in the oppositewall of the sleeve, whereby said sleeve forms an acoustic filter capableof absorbing vibratory air pressure variations while allowing steady aircurrents to pass to t e outside and a helical spring disposed betweenthe perforated wall portions of said sleeve.

3. In a device of the character described, a tubular member adapted tohave one end thereof detachably secured to the opening of a telephonetransmitter, a mouthpiece secured to the other end of said member beingconstituted by a closed double walled sleeve of easily yielding materialcapable of adapting itself to the mouth of a user, a collar within saidsleeve to provide two communicating chambers, the chamber adjacent tosaid tubular member having portholes in the inner and ouer wallsthereof, whereby said sleeve forms an acoustic filter absorbingvibratory air pressure variations at the rate of the higher speechfrequencies, while allowing low frequency and constant air currents topass to the outside, and resilient stiffening means disposed between thewalls of said chamber adjacent to said tubu lar member.

HELENE SCHOBER,

MAIDEN-NAME MOERDER.

